1. Field of the Invention
The present invention relates to an industrial two-layer fabric suited for use in the manufacture of paper or nonwoven fabric requiring a uniform water drainage property, dehydration property, breathability, supporting property of articles to be conveyed, and the like.
2. Description of the Related Art
Fabrics made by weaving warps and wefts are used widely for industrial fabrics and, for example, papermaking fabrics, conveying belts, and filter cloths. They are required to have fabric properties suited for using purposes or using environments. Requirements for papermaking fabrics used in a papermaking water removal step from raw materials by utilizing meshes of the fabrics are especially strict.
Such fabrics are required to have, for example, excellent surface smoothness so as not to easily transfer the fabric's wire mark to the supported paper, a dehydration property to enable complete and uniform removal of excess water contained in the raw materials, sufficient rigidity and wear resistance to enable suitable use of the fabric even under severe environments, and a capacity to retain conditions necessary for making excellent paper for a long period of time. Fabrics are also required to have a fiber supporting property, capacity to improve a papermaking yield, size stability, traveling stability, and the like. The demand for papermaking fabrics has become severer with a recent increase in the speed of papering machines.
Among industrial fabrics, papermaking fabrics must satisfy the most severe requirements so that a description of them will promote understanding of the requirements for most of the industrial fabrics and solutions thereof. Therefore, the papermaking fabrics will hereinafter be described as one example.
With a recent increase in the speed of the papermaking machine, industrial fabrics are required to have a particularly excellent dehydration property and surface smoothness. Although necessary dehydration characteristics differ, depending on the machine or product to be manufactured using the fabric, a dehydration property and fiber supporting property are essential conditions for any product. With recent increased use of waste paper containing many minute fibers, much importance has been given to the fiber supporting property. In addition, the fabrics are required to have an excellent dehydration property because sheet formation using minute fibers leads to deterioration in dehydration property.
In papermaking fabrics, it is the common practice to carry out centrifugation, press dehydration and the like by making use of meshes of the fabrics. In order to achieve sufficient water dehydration, suction dehydration from the backside surface of the meshes is also carried out. Necessary characteristics such as fiber supporting property and dehydration property have a great influence on the operation efficiency and running cost.
Papermaking raw materials are supplied onto a wire running from a head box so that fibers tend to be oriented in a machine direction. In order to improve the fiber supporting property, it is recommended to form a fabric having a fine surface and a weft long crimp structure. This is because if fibers oriented in a machine direction are received by a warp long crimp structure, the fibers tend to drop off between warps.
U.S. Pat. No. 5,641,001 discloses a fabric for satisfying both requirements, that is, the fiber supporting property and dehydration property.
This fabric has an additional weft of a small diameter between wefts. FIG. 8 of U.S. Pat. No. 5,641,001 shows a plan view of the surface of the fabric in which additional wefts that extend in a cross oblique direction are arranged. Since additional wefts of a small diameter are placed between wefts, the fabric is excellent in surface smoothness, fiber supporting property, and dehydration property.